Kidney regeneration: any prospects?

Chronic kidney disease is a leading cause of mortality and morbidity in western countries which affects about 11% of the adult population. With the increasing rate of chronic kidney disease and limited alternatives for its treatment, potential regenerative approaches for kidney damage are urgently needed, but are limited by the complexity of this organ. Bone marrow-derived stem cells as well as mesenchymal stem cells were envisioned for the development of this type of treatment. However, most studies suggested that these cells cannot differentiate into renal epithelial cells, and concluded that their beneficial effects are probably related to secretion of growth factors. In addition, a long-term partial maldifferentiation of injected mesenchymal stem cells into adipocytes accompanied by glomerular sclerosis was reported. The incapacity of bone marrow-derived stem cells to differentiate into renal cells suggested that turnover of resident renal epithelial cells may be related to the existence of potential stem/progenitor cells within the adult human kidney. Consistently, renal progenitors with the potential to differentiate into podocytes as well as tubular cells were recently identified at the urinary pole of the Bowman's capsule in adult kidneys. The discovery of renal progenitors that encourage regeneration and promote functional repair of glomerular injury demonstrates that prevention and treatment of glomerulosclerosis may be possible. In addition, converging evidence suggests that the outcome of glomerular disorders depends on a balance between injury and regeneration provided by renal progenitors. In summary, understanding how self-renewal and fate decision of renal progenitors may be perturbed or modulated will be of crucial importance to obtain novel pharmacological tools for prevention and treatment of diabetic nephropathy, as well as other causes of glomerulosclerosis.